Determination of the association of GHR/AluI gene polymorphisms with milk yield traits in Holstein and Jersey cattle raised in Turkey.

Abstract This research was carried out to determine the effect of a specific single nucleotide polymorphism (SNP) region in exon 10 of the growth hormone receptor (GHR) gene on milk production traits in Jersey and Holstein cows raised in Turkey. Milk samples were recorded as a test day milk yield (TDMY) and an adjusted based 305 d milk yield (305-DMY). Also, milk component traits were detected. Based on the scope of this study, a total of 748 dairy cows, including 305 Holsteins raised in the Marmara Region and 163 Holstein and 280 Jersey raised in the Black Sea Region, were genotyped for the GHR gene using the RFLP-PCR technique. Jersey cows carrying the GG genotype (5.24 %) were associated with higher fat content (P<0.05). Jersey cows with GG and AG also had a higher protein content (3.44 % and 3.38 %, respectively) (P<0.05). Similarly, the protein content was the highest in Holstein cows with the GG genotype (3.46 %) (P<0.01), whereas Holstein cows having AA genotypes displayed higher TDMY (24.64 kg/d) (P<0.05) and 305-DMY (8472.4 kg) (P<0.01). The estimated increase in milk protein and fat contents due to the G allele was 0.07 % and 0.22 % in the Jersey breed, respectively. On the other hand, allele A was highly related to an increase in protein yield and 305-DMY of 0.04 and about 675 kg in the Holstein breed, respectively. The GHR gene should be considered as a potential candidate gene in marker-assisted selection programs to improve the performance of milk and related traits in Turkey dairy cattle populations.